[Discuss-gnuradio] How can i determine my current phone's frequency?

Hi guys,
I want to know which frequency my cellular phone is using (for uplink - UMTS).
I'm using USRP B210, i tried the spectrum analyzer tool but i don't really know what to expect- isn't the transmitting power of my cellular supposed to be higher (in a single frequency) than all other frequencies? 
my goal is to try and see if i can notice a change in dB when i get my phone closer/further to the B210.

Thanks a lot,

Meny